Devices of the abovementioned type are particularly if not exclusively used in packaging lines for confectionery products, such as chocolate bars, biscuits or others of similar type in which such products are moved on transport lines arranged in ranks or groups of ranks spaced apart (in this context by ranks are meant rows of products in line, in which these lines are arranged perpendicularly to the direction of advance of the products). Between these transport lines and the packaging machines there is typically an intermediate buffer for the accumulation of products, whose main function is to ensure a regular feed to the packaging machine at a predetermined uniform rate and thus render the feed independent of the speed of the ranks arriving and variations in their flow.
With such accumulation buffers it is then possible to effectively feed different automatic packaging lines at speeds and feed rates programmed in relation to the nature of the products being processed.
One example of such a device for the accumulation and release of products is known from the international patent application published under no. WO2004/087543 in the name of the same Applicant.
Typically these accumulation devices comprise a store within which a plurality of container elements are supported and conveyed along a path which optimises the accumulation capacity. Each container comprises a plurality of shelves capable of supporting and containing corresponding ranks of the products fed to the buffer.
The path along which the containers move within the buffer is selected in such a way that each container is sequentially led to a receiving opening to load one or more ranks of the products arriving at the buffer on each of the shelves and at the same time or not at the same time a previously loaded container is passed by appropriate conveyance means, for example of the chain type, to the delivery or discharge opening for release of the products leaving the buffer.
A typical path for the movement of containers in the buffer capable of optimising accumulation capacity provides for an ascending vertical section in which containers are loaded in sequence through the receiving opening and an opposite and parallel descending vertical section in which the containers are conveyed to the delivery opening in order to discharge products from the buffer. These two vertical sections are connected by corresponding respective horizontal sections to define an overall path of a square shape with pairs of opposite sections parallel to each other as for example illustrated in the earlier PCT patent application mentioned above. Containers filled with products are accumulated side by side in the upper horizontal section while containers which have previously been emptied are accumulated again side by side in the lower horizontal section.
In this type of device provision is also made on discharging from the buffer for pusher means for moving the ranks of products from each supporting plane in the container being emptied onto an outgoing conveyor belt. The pusher means is therefore designed to move transversely to the direction of movement of the container being discharged, backwards and forwards with respect to the same, along a first course in one direction to come into contact with the rank of products which have to be discharged and then again moved away from the container along a return course in the opposite direction. Obviously the fact that these stages in movement of the pusher means must be repeated for each shelf in the container has an effect on the speed and rate at which the ranks of products are discharged, and therefore constitutes a limit to the overall productivity of the unit, which in such applications cannot be reconciled with high speeds (understood as the number of ranks delivered per unit time) expected downstream from the accumulation buffer in the packaging lines.
Another similar limitation which is encountered in devices of the known type is associated with the speed with which the buffer is fed, which in this case is influenced by the times required for moving the container being loaded and the frequency with which the ranks loaded in sequence are fed to the shelves of a given container.